The purpose of this project is to identify clinical, radiologic, and behavioral patterns in the use of radiologic diagnostic procedures for the detection of colorectal cancer. In the forthcoming year, we will concentrate our research in four primary areas: 1) Extensive analysis on epidemiologic, signs and symptoms, and diagnostic data collected on 3000 barium enema examinations administered over a four month period in community hospitals across the mid-Michigan area. Standard frequency and contingency methods as well as pattern detection techniques will be used to identify groups of patients at risk for colon cancer and to increase the yield of positive examinations. 2) Continuing investigation of physician behavior in ordering the barium enema examination, with the hopes of developing an algorithm for optimal use of the exam. 3) Further investigation of factors influencing false-negative examinations and the establishment of an information system combining our results with selected Cancer Registry data for use by community hospitals across Michigan. 4) Cost estimates computation and definition of optimal economic use of radiologic diagnostic procedures. The information obtained from these studies will be used to recommend additional guidelines for the control and management of colorectal cancer.